Remove loaders from the pools for the normal scenario

immer/extra/persist/alias.hpp

@@ -18,10 +18,8 @@ struct type_alias
     {
     }
 
-    friend bool operator==(const type_alias& left, const type_alias& right)
-    {
-        return left.value == right.value;
-    }
+    friend bool operator==(const type_alias& left,
+                           const type_alias& right) = default;
 
     /**
      * This works only starting with fmt v10.

immer/extra/persist/box/pool.hpp

@@ -64,10 +64,8 @@ struct input_pool
 {
     immer::vector<immer::box<T, MemoryPolicy>> boxes;
 
-    friend bool operator==(const input_pool& left, const input_pool& right)
-    {
-        return left.boxes == right.boxes;
-    }
+    friend bool operator==(const input_pool& left,
+                           const input_pool& right) = default;
 
     template <class Archive>
     void load(Archive& ar)

immer/extra/persist/champ/pool.hpp

@@ -165,10 +165,7 @@ struct container_input_pool
     nodes_load<T, champ_t::bits> nodes;
 
     friend bool operator==(const container_input_pool& left,
-                           const container_input_pool& right)
-    {
-        return left.nodes == right.nodes;
-    }
+                           const container_input_pool& right) = default;
 
     template <class Archive>
     void load(Archive& ar)

immer/extra/persist/common/pool.hpp

@@ -42,10 +42,8 @@ struct values_load
     {
     }
 
-    friend bool operator==(const values_load& left, const values_load& right)
-    {
-        return left.data == right.data;
-    }
+    friend bool operator==(const values_load& left,
+                           const values_load& right) = default;
 };
 
 template <class Archive, class T>

immer/extra/persist/json/json_immer.hpp

@@ -263,8 +263,16 @@ class json_immer_input_archive
     {
     }
 
-    Pools& get_input_pools() { return pools; }
-    const Pools& get_input_pools() const { return pools; }
+    template <class Container>
+    auto& get_loader()
+    {
+        auto& loader = loaders[boost::hana::type_c<Container>];
+        if (!loader) {
+            const auto& type_pool = pools.template get_pool<Container>();
+            loader.emplace(type_pool.pool, type_pool.transform);
+        }
+        return *loader;
+    }
 
     template <class T>
     friend void prologue(json_immer_input_archive& ar, T&& v)
@@ -322,10 +330,15 @@ class json_immer_input_archive
         CEREAL_LOAD_FUNCTION_NAME(ar.previous, st);
     }
 
+    bool ignore_pool_exceptions = false;
+
 private:
     WrapF wrap;
     Previous previous;
     Pools pools;
+
+    using Loaders = decltype(Pools::generate_loaders());
+    Loaders loaders;
 };
 
 } // namespace immer::persist

immer/extra/persist/json/json_with_pool.hpp

@@ -113,20 +113,53 @@ struct output_pools
     }
 };
 
+template <class Derived, class Loader>
+struct no_loader
+{};
+
+template <class Derived, class Loader>
+struct with_loader
+{
+    std::optional<Loader> loader;
+
+    auto& get_loader_from_per_type_pool()
+    {
+        if (!loader) {
+            auto& self = static_cast<Derived&>(*this);
+            loader.emplace(self.pool, self.transform);
+        }
+        return *loader;
+    }
+};
+
+/**
+ * A pool for one container type.
+ * Normally, the pool does not contain a loader, which is located inside the
+ * json_immer_input_archive.
+ *
+ * But in case of transformations, there is no json_immer_input_archive involved
+ * and it becomes convenient to have the corresponding loader stored here, too,
+ * via with_loader.
+ */
 template <class Container,
           class Pool       = typename container_traits<Container>::input_pool_t,
           class TransformF = boost::hana::id_t,
-          class OldContainerType = boost::hana::id_t>
+          class OldContainerType                    = boost::hana::id_t,
+          template <class, class> class LoaderMixin = no_loader>
 struct input_pool
+    : LoaderMixin<input_pool<Container,
+                             Pool,
+                             TransformF,
+                             OldContainerType,
+                             LoaderMixin>,
+                  typename container_traits<
+                      Container>::template loader_t<Pool, TransformF>>
 {
     using container_t     = Container;
     using old_container_t = OldContainerType;
 
     Pool pool = {};
     TransformF transform;
-    std::optional<typename container_traits<
-        Container>::template loader_t<Pool, TransformF>>
-        loader;
 
     input_pool() = default;
 
@@ -142,27 +175,6 @@ struct input_pool
     {
     }
 
-    input_pool(const input_pool& other)
-        : pool{other.pool}
-        , transform{other.transform}
-    {
-    }
-
-    input_pool& operator=(const input_pool& other)
-    {
-        pool      = other.pool;
-        transform = other.transform;
-        return *this;
-    }
-
-    auto& get_loader()
-    {
-        if (!loader) {
-            loader.emplace(pool, transform);
-        }
-        return *loader;
-    }
-
     template <class Func>
     auto with_transform(Func&& func) const
     {
@@ -174,8 +186,8 @@ struct input_pool
                 func))>;
         using TransF = std::function<new_value_type(const value_type&)>;
         // the transform function must be filled in later
-        return input_pool<NewContainer, Pool, TransF, Container>{pool,
-                                                                 TransF{}};
+        return input_pool<NewContainer, Pool, TransF, Container, with_loader>{
+            pool, TransF{}};
     }
 
     friend bool operator==(const input_pool& left, const input_pool& right)
@@ -187,6 +199,12 @@ struct input_pool
     {
         pool.merge_previous(original.pool);
     }
+
+    static auto generate_loader()
+    {
+        return std::optional<typename container_traits<
+            Container>::template loader_t<Pool, TransformF>>{};
+    }
 };
 
 /**
@@ -230,20 +248,18 @@ class input_pools
     {
     }
 
-    bool ignore_pool_exceptions = false;
-
     auto& storage() { return storage_(); }
     const auto& storage() const { return storage_(); }
 
     template <class Container>
-    auto& get_loader()
+    const auto& get_pool()
     {
         using Contains =
             decltype(hana::contains(storage(), hana::type_c<Container>));
         if constexpr (!Contains::value) {
             auto err = error_missing_pool_for_type<Container>{};
         }
-        return storage()[hana::type_c<Container>].get_loader();
+        return storage()[hana::type_c<Container>];
     }
 
     template <class OldContainer>
@@ -261,7 +277,7 @@ class input_pools
         if constexpr (!IsJust::value) {
             auto err = error_missing_pool_for_type<OldContainer>{};
         }
-        return storage()[Key{}.value()].get_loader();
+        return storage()[Key{}.value()].get_loader_from_per_type_pool();
     }
 
     template <class Archive>
@@ -353,7 +369,8 @@ class input_pools
                     auto err = error_missing_pool_for_type<
                         typename decltype(new_type)::type>{};
                 }
-                auto& loader = get_data()[new_type].get_loader();
+                auto& loader =
+                    get_data()[new_type].get_loader_from_per_type_pool();
                 return loader.load(id);
             };
         };
@@ -395,6 +412,20 @@ class input_pools
             s[key].merge_previous(original_s[key]);
         });
     }
+
+    static auto generate_loaders()
+    {
+        using Storage = std::decay_t<decltype(std::declval<StorageF>()())>;
+        using Types   = decltype(hana::keys(std::declval<Storage>()));
+        auto storage =
+            hana::fold_left(Types{}, hana::make_map(), [](auto map, auto type) {
+                using TypePool =
+                    std::decay_t<decltype(std::declval<Storage>()[type])>;
+                return hana::insert(
+                    map, hana::make_pair(type, TypePool::generate_loader()));
+            });
+        return storage;
+    }
 };
 
 inline auto generate_output_pools(auto type_names)
@@ -468,11 +499,11 @@ auto load_pools(std::istream& is, const auto& wrap)
 {
     const auto reload_pool =
         [wrap](std::istream& is, Pools pools, bool ignore_pool_exceptions) {
-            auto restore                 = immer::util::istream_snapshot{is};
-            const auto original_pools    = pools;
-            pools.ignore_pool_exceptions = ignore_pool_exceptions;
+            auto restore              = immer::util::istream_snapshot{is};
+            const auto original_pools = pools;
             auto ar = json_immer_input_archive<Archive, Pools, decltype(wrap)>{
                 std::move(pools), wrap, is};
+            ar.ignore_pool_exceptions = ignore_pool_exceptions;
             /**
              * NOTE: Critical to clear the pools before loading into it
              * again. I hit a bug when pools contained a vector and every

immer/extra/persist/json/persistable.hpp

@@ -50,24 +50,8 @@ struct persistable
     {
     }
 
-    persistable(const persistable& other)
-        : container{other.container}
-    {
-    }
-
-    persistable& operator=(const persistable&) = default;
-
-    persistable(persistable&& other)
-        : container{std::move(other.container)}
-    {
-    }
-
-    persistable& operator=(persistable&&) = default;
-
-    friend bool operator==(const persistable& left, const persistable& right)
-    {
-        return left.container == right.container;
-    }
+    friend bool operator==(const persistable& left,
+                           const persistable& right) = default;
 
     // template <std::enable_if_t<detail::is_iterable<Container>, bool> = true>
     // friend auto begin(const persistable& value)
@@ -131,7 +115,6 @@ void load_minimal(
 {
     auto& loader =
         const_cast<json_immer_input_archive<Previous, Pools, WrapF>&>(ar)
-            .get_input_pools()
             .template get_loader<Container>();
 
     // Have to be specific because for vectors container_id is different from
@@ -142,7 +125,7 @@ void load_minimal(
     try {
         value.container = loader.load(container_id_{id});
     } catch (const pool_exception& ex) {
-        if (!ar.get_input_pools().ignore_pool_exceptions) {
+        if (!ar.ignore_pool_exceptions) {
             throw ::cereal::Exception{fmt::format(
                 "Failed to load a container ID {} from the pool of {}: {}",
                 id,